Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/28—Dragees; Coated pills or tablets, e.g. with film or compression coating
  • A61K9/2806—Coating materials
  • A61K9/2833—Organic macromolecular compounds
  • A61K9/284—Organic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyvinyl pyrrolidone
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/13—Amines
  • A61K31/155—Amidines (), e.g. guanidine (H2N—C(=NH)—NH2), isourea (N=C(OH)—NH2), isothiourea (—N=C(SH)—NH2)
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/2004—Excipients; Inactive ingredients
  • A61K9/2022—Organic macromolecular compounds
  • A61K9/2027—Organic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyvinyl pyrrolidone, poly(meth)acrylates
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/20—Pills, tablets, discs, rods
  • A61K9/28—Dragees; Coated pills or tablets, e.g. with film or compression coating
  • A61K9/2806—Coating materials
  • A61K9/2833—Organic macromolecular compounds
  • A61K9/286—Polysaccharides, e.g. gums; Cyclodextrin
  • A61K9/2866—Cellulose; Cellulose derivatives, e.g. hydroxypropyl methylcellulose
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/14—Particulate form, e.g. powders, Processes for size reducing of pure drugs or the resulting products, Pure drug nanoparticles
  • A61K9/141—Intimate drug-carrier mixtures characterised by the carrier, e.g. ordered mixtures, adsorbates, solid solutions, eutectica, co-dried, co-solubilised, co-kneaded, co-milled, co-ground products, co-precipitates, co-evaporates, co-extrudates, co-melts; Drug nanoparticles with adsorbed surface modifiers
  • A61K9/145—Intimate drug-carrier mixtures characterised by the carrier, e.g. ordered mixtures, adsorbates, solid solutions, eutectica, co-dried, co-solubilised, co-kneaded, co-milled, co-ground products, co-precipitates, co-evaporates, co-extrudates, co-melts; Drug nanoparticles with adsorbed surface modifiers with organic compounds

Definitions

• the present invention relates to an extended release pharmaceutical tablet containing metformin as an active substance.
• the ideal dosage regimen is that by which an acceptable therapeutic concentration of drug at the site(s) of action is attained immediately and is then maintained constant for the duration of the treatment.
• Providing dose size and frequency of administration are correct, therapeutic 'steady-state' plasma concentrations of a drug can be achieved promptly and maintained by the repetitive administration of conventional peroral dosage forms.
• conventional peroral dosage forms there are a number of potential limitations associated with conventional peroral dosage forms.
• Oral ingestion is the traditionally preferred route of drug administration, providing a convenient method of effectively achieving both local and systemic effects.
• An ideal oral drug delivery system should steadily deliver a measurable and reproducible amount of drug to the target site over a prolonged period.
• Controlled-release (CR) delivery systems provide a uniform concentration/amount of the drug at the absorption site and thus, after absorption, allow maintenance of plasma concentrations within a therapeutic range, which minimizes side effects and also reduces the frequency of administration.
• CR products are formulations that release active drug compounds into the body gradually and predictably over a 12- to 24-hour period and that can be taken once or twice a day.
• these products provide numerous benefits compared with immediate-release drugs, including greater effectiveness in the treatment of chronic conditions, reduced side effects, greater convenience, and higher levels of patient compliance due to a simplified dosing schedule. Because of the above advantages, such systems form the major segment of the drug delivery market.
• Extended-release tablets have been described in the prior art and many methods have been used to provide extended-release pharmaceutical dosage forms in order to maintain therapeutic serum levels of medicaments and to minimize the effects of missed doses of drugs caused by a lack of patient compliance.
• Osmotic systems for example, utilize osmotic pressure as the driving force for the delivery of drugs.
• osmotic pressure As the driving force for the delivery of drugs.
• it consists of an osmotic core (a drug with or without an osmagent), which is coated with a semipermeable membrane, and a delivery orifice is created with a mechanical or laser drill.
• EOP elementary osmotic pump
• US Pat. No. 6,099,859 teaches an osmotic device wherein the active agent, metformin hydrochloride, is released from a core surrounded by a semipermeable membrane which is impermeable to the active agent.
• the semipermeable membrane contains within it a flux enhancer, which, according to the disclosure, can be a water soluble material or an enteric material.
• the flux enhancing agent dissolves or leaches from the semipermeable membrane to form paths in the semipermeable membrane for the fluid to enter the core and dissolve the active ingredient.
• the semipermeable membrane may also have an orifice formed by a mechanical or laser drill.
• the push-pull osmotic pump which is a bilayer tablet and is suitable for the delivery of highly or poorly water-soluble drugs.
• the upper layer consists of a drug along with osmotic agents.
• the lower layer consists of polymeric osmotic agents.
• the tablet is coated with a semi-permeable membrane, and a delivery orifice is created similar to that of an EOP.
• the push-pull osmotic system is described in for example US Pat. Nos. 4,612,008 and 5,082,668. Examples of the push-pull osmotic system products developed by Alza Corporation include Ditropan XL, Glucotrol XL and Procardia XL.
• a major disadvantage of the above-described systems is that mechanical or laser drilling is capital intensive. Also, the size of the hole is critical. Further, the integrity and consistency of the coating is essential. If the coating process is not well controlled there is a risk of film defects, which could result in dose dumping and the film droplets must be induced to coalesce into a film with consistent properties.
• MODAS or Multiporous Oral Drug Absorption System developed by Elan Corporation is surrounded by a non-disintegrating, timed-release coating, which after coming in contact with gastrointestinal fluid is transformed into semipermeable membrane through which the drug diffuses in a rate-limiting manner.
• the tablet consists of a core of active drug plus excipients. This is then coated with a solution of insoluble polymers and soluble excipients (pore-forming agents). After ingestion, the fluid of the gastrointestinal tract dissolves the soluble excipients in the outer coating leaving just the insoluble polymer, thereby forming a network of tiny, narrow channels connecting fluid from the Gl tract to the inner drug core of water-soluble drug.
• This fluid passes through these channels into the core, dissolves the drug, and a resultant solution of drug diffuses out in a controlled manner to the outside.
• excipients such as buffers can help produce a microenvironment within the tablet that facilitates more predictable release rates and absorption.
• the MODAS is described in for example US Pat. No. 5,505,962.
• a disadvantage of the MODAS is that the coating, since it requires a pore forming agent, cannot provide a uniform coating and therefore the release rate may not be uniform from one tablet to another.
• US Pat. No. 5,955,106 describes a pharmaceutical composition containing metformin as an active substance and a hydrocolloid-forming agent as a retardant.
• hydrocolloid-forming agents as retardants is based on the property of the hydrocolloid-forming agent to swell and form a gel matrix when it is contacted with a release medium or digestive juices. The matrix erodes to release the active substance.
• the interaction between the amount of hydrocolloid-forming agent and the degree of viscosity determines the time course of release.
• an extended release pharmaceutical tablet comprising:
• a core comprising by weight, based on the core weight, about 70% to about 99% metformin and pharmaceutically acceptable excipients
• a coating permeable to metformin said tablet exhibiting a dissolution profile such that after about 2 hours, from about 7% to about 60% of the metformin is released; after about 4 hours, from about 15% to about 90% of the metformin is released; after about 8 hours, from about 50% to about 100% of the metformin is released; after about 12 hours, more than about 75% of the metformin is released.
• the invention provides a coating consisting essentially of a water-insoluble, water-permeable film-forming polymer; a water- soluble polymer and a plasticizer and is free of monomeric pore-forming agent.
• the coating consists essentially by weight, based on the coating weight, from about 20% to about 85% of water-insoluble, water-permeable film- forming polymer, from about 10% to about 75% of water-soluble polymer and from about 3% to about 40% plasticizer.
• the coating consists essentially by weight, based on the coating weight from about 50% to about 85% of water- insoluble, water-permeable film-forming polymer, from about 10% to about 35% of water-soluble polymer and form about 3% to about 15% of plasticizer.
• the water-insoluble, water-permeable polymer is ethylcellulose
• the water- insoluble polymer is polyvinylpyrrolidone.
• a preferred plasticizer is selected from the group consisting of stearic acid and dibutyl sebacate.
• the pharmaceutical excipients comprise glyceryl behenate, polyvinylalcohol and silicon dioxide.
• the core may further comprise an expanding agent. If an expanding agent is present, it is present preferably in an amount from about 3% to about 25% of the core dry weight.
• the expanding agent is preferably a non-hydrocolloid. More preferably, the non-hydrocolloid is crospovidone.
• FIG. 1 is a graph depicting the dissolution profile of the formulations described in Example 4.
• FIG. 2 is a graph depicting the dissolution profile of a formulation having a core of the present invention with or without the expanding agent Crospovidone coated with the semi-permeable membrane as taught in US Patent No. 6,099,859.
• the invention provides a tablet comprising a core and a coating.
• the core includes metformin or a pharmaceutically acceptable salt thereof and conventional excipients, for example a lubricant, and a binder and/or a filler, and optionally a glidant.
• the tablet may contain other pharmaceutically acceptable excipients in the core and/or the coating.
• lubricants include stearic acid, magnesium stearate, glyceryl behenate, stearyl behenate, talc, mineral oil (in polyethylene glycol), and sodium stearyl fumarate etc. Glyceryl behenate is the preferred lubricant.
• binders include water-soluble polymer, such as modified starch, gelatin polyvinylpyrrolidone, polyvinylalcohol (PVA), etc.
• the preferred binder is polyvinylalcohol.
• fillers include lactose, microcrystalline cellulose, etc., the latter being preferred.
• An example of a glidant is silicon dioxide (Aerosil® of Degussa).
• the above binders, lubricants, fillers glidants, and any other excipient that may be present can further be found in the relevant literature, for example in the Handbook of Pharmaceutical Excipients.
• the relative amounts of ingredients in the core are preferably as follows.
• the proportion of metformin in the core may vary between about 70% and about 90%, preferably about 85% and about 98%, of the core dry weight.
• the proportion of lubricant and/or glidant in the core may vary between about 0.3% and about 10%, preferably about 0.5% to about 3%, of the core dry weight.
• the proportion of binder or filler in the core may vary between about 0.5% and about 25%, preferably about 1 % to about 10%, of the core dry weight.
• the core may further comprise, according to one embodiment of the invention, an expanding agent.
• the expanding agent may be either a hydrocolloid or a non-hydrocolloid. The expanding agent will lead to an expansion of e.g. from about 10% to about 35% vol., especially from about 15% to about 30% vol.
• hydrocolloid agent Na starch glycolate (Primogel®); any agent that swells with water can also be used e.g., known disintegrant agents.
• Suitable non- hydrocolloid agents are for example insoluble polyvinylpolypyrrolidones such as Crospovidone (Kollidon CL®), polacrilin potassium (Amberlite® IRP 88) and microcrystalline cellulose (Avicel®).
• the preferred expanding agent is Crospovidone.
• the proportion of expanding agent, when one is present, in the core may vary between from about 3% and about 25%, preferably from about 5% to about 20%, of the core dry weight.
• Tablets according to the invention can be prepared through various manufacturing processes known in the art.
• a manufacturing process for preparing a core according to the invention is as follows. Metformin is first granulated with a binder, in a granulator, preferably but not necessarily a fluidized bed granulator. The binder is first dissolved or dispersed in a suitable solvent, preferably water. The solution or suspension of binder is then sprayed onto the drug in a granulator, e.g. fluidized bed granulator.
• a granulator e.g. fluidized bed granulator.
• fluidized bed granulators manufactured by Glatt (Germany) or Aeromatic (Switzerland) can be used for this operation.
• Another exemplary process involves the use a conventional or high shear mixer to proceed granulation.
• the drug can be mixed with a filler, prior to the granulation step.
• Granules once dried can be mixed with the other excipients, especially with the lubricant and the expanding agent if present, but also with glidants and any other excipient suitable to improve processing.
• the mixture of granules (preferably with lubricant), and optionaly glidant is pressed into tablets.
• the active ingredient and lubricant and/or glidant and/or expanding agent can be mixed with a suitable filler and compressed into tablets (the expanding agent may also be added at that stage). Also, it is possible to mix the active ingredient and the lubricant (e.g.
• glyceryl behenate e.g. a fluidized bed granulator
• a granulator e.g. a fluidized bed granulator
• Tablets can be obtained by standard techniques, e.g. on a (rotary) press (for example Manesty Betapress®) fitted with suitable punches.
• the resulting tablets are hereinafter referred as tablet cores.
• These tablet cores are then coated with a coating designed to achieve an extended release of metformin.
• the coating comprises a water-insoluble, water-permeable film-forming polymer, together with a plasticizer and a water- soluble polymer.
• the coating disclosed herein is permeable to metformin. It is well known in the art that varying the ratios of the water-insoluble, water-permeable film-forming polyme ⁇ water-soluble polymer can alter the permeability of the coating and hence alter the release of metformin. Additionally, the presence or absence of an expanding agent in the tablet cores will also influence the permeability of the coat to metformin.
• the ratio of water-insoluble, water-permeable film-forming polymer:water-soluble polyme ⁇ plasticizer may have to be changed depending on the presence or absence of an expanding agent in the tablet core.
• Plasticizers are used to make the coat elastic and pliable.
• the amount and choice of the plasticizer contribute to the hardness of the final tablet and may even affect its dissolution or disintegration characteristics, as well as its physical and chemical stability.
• the presence of an expanding agent in the tablet core will increase the mechanical pressure exerted on the coat and accordingly the amount of plasticizer in the coat should be increased to make the coat more pliable as the coat will otherwise break.
• the ratio of water-insoluble, water-permeable film-forming polyme ⁇ water-soluble polymer:plasticizer taught herein is permeable to metformin and is free of pore-forming agent.
• the water-insoluble, water-permeable film-forming polymer can be a cellulose ether, such as ethylcellulose, a cellulose ester, such as cellulose acetate, etc.
• a preferred film-forming polymer is ethylcellulose (available from Dow Chemical under the trade name Ethocel®).
• the palsticizer can be ester such as a citrate ester or dibutyl sebacate, an oil such as castor oil, a polyalkyleneglycol such as polyethyleneglycol of various molecular weights, a fatty acid such as stearic acid.
• the preferred plasticizers are dibutyl sebabcate and stearic acid.
• the water-soluble polymer is preferably polyvinylpyrrolidone.
• Some other excipients can be used in the coating, as for example acrylic acid derivatives (for example those available from Roehm Pharma under the trade name Eudragit®), pigments, etc.
• the relative amounts of ingredients in the coating are preferably as follows.
• the proportion of water-insoluble, water-permeable polymer (e.g. ethylcellulose) in the coating may vary between about 20% and about 85% of the coating dry weight.
• the proportion of water-soluble polymer (e.g. polyvinylpyrrolidone) in the coating may vary between about 10% and about 75% of the coating dry weight.
• the proportion of plasticizer e.g.
• stearic acid in the coating may vary from about 3% and about 40% of the coating dry weight.
• the relative proportions of the ingredients notably the ratio of water-insoluble, water- permeable film-forming polymer to water-soluble polymer and to plasticizer, can be varied depending on the release profile to be obtained (a more extended release is generally obtained with a higher amount of water-insoluble, water-permeable film forming polymer) and the presence of an expanding agent in the core (which usually leads to more plasticizer and less water-insoluble, water-permeable film forming polymer).
• the coating process can be as follows. Ethylcellulose, dibutyl sebacate (or stearic acid) and polyvinylpyrrolodone are dissolved in a solvent such as ethanol. The resulting solution is sprayed onto the tablet cores, using a coating pan or a fluidized bed apparatus.
• the weight ratio of coating/tablet core is comprised e.g.
• the tablet comprises an amount of metformin that can vary within broad limits, such as from about 400mg to about 2000mg.
• this amount can be from about 550 mg to about 2000 mg per tablet, with exemplary ranges being about: 600mg-1800mg; 700mg-1500mg; 800mg-1300mg; 900mg-1100mg; especially about 1000mg.
• this amount can be from about 400mg to about 550mg; especially about 500mg.
• the invention thus provides a metformin extended release tablet free of stabilizer and free of pore-forming agent, exhibiting a dissolution profile such that after 2 hours, form about 7% to about 60% of the metformin is released; after about 4 hours, from about 15% to about 90% of the metformin is released; after about 8 hours, form about 50% to about 100% of the metformin is released; after about 12 hours, more than about 75% of the metformin is released.
• the dissolution profile is such that after about 2 hours, from about 10% to about 40% of the metformin is released; after about 4 hours, from about 20% to about 65% of the metformin is released; after about 8 hours, from about 50% to about 100% of the metformin is released; after about 12 hours, more than about 75% of the metformin is released.
• the dissolution profile is such that after about 2 hours, from about 40% to about 60% of the metformin is released; after about 4 hours, from about 65% to about 90% of the metformin is released; after about 8 hours, from about 85% to about 100% of the metformin is released; after about 12 hours, more than about 90% of the metformin is released.
• Examples of preferred metformin tablets according to the invention include a tablet composition comprising:
• a core comprised of metformin, polyvinylalcohol, silicon dioxide and glyceryl behenate;
• a coating comprised of ethylcellulose, polyvinylpyrrolidone and stearic acid or dibutyl sebacate.
• Another preferred tablet composition is one in which the core additionally comprises an expanding agent.
• the expanding agent is preferably a non-hydro colloid expanding agent.
• the non-hydro colloid expanding agent is an insoluble polyvinylpolypyrrolidone such as Crospovidone (Kollidon-CL®).
• Metformin and silicon dioxide are placed in a fluidized bed apparatus.
• An aqueous PVA solution (at 1% by weight) is sprayed to get granules.
• the apparatus is a Glatt GPCG1, operated with the following parameters:
• Ethocel, povidone and stearic acid are first dissolved in denatured alcohol (550g).
• the coating solution is then sprayed onto the tablet cores in a coating pan (Vector LCDS), with the following spraying parameters:
• Stability data [0037] Storage conditions: conforms to USP 23 guidline (25°C and 60% relative humidity and 40°C and 75% relative humidity). The results show that the metformin composition of this example is stable.
• Example 1A is reproduced according to the same manufacturing process described above, with the following formulation in the core:
• the coating has the following formulation:
• Example 1A reproduced, but with the following coating formulation:
• Example 1 B is reproduced, but with the following coating formulation:
• Example 3A is reproduced according to the same manufacturing process as Example 1 A with the following formulation in the core:
• the coating has the following formulation:
• One advantage of the invention is that it provides sustained release tablet with vastly improved dissolution properties without the need for a coating having preformed pores.
• a coating having preformed pores In order to illustrate the advantage of the coatings according to the invention which do not require preformed pores to provide the

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